Need carbs overhauled on 1994 Sea Doo GTX

[Rivergator]

I have a set of dual carbs (I assume they are Mikunis) with Vortex flame arrestors on my 1994 GTX. The Doo has been sitting for 3 years due to needed repairs. Now I am trying to get it started and it will start with starter fluid, but it runs badly and stalls in low rpm. At midrange to high rpm the engine back fires here and then. I have flushed the carbs with all kinds of miracle products, but the rough running and sputtering is about a good as it gets, I guess. I assume my carbs need a good going over, but I am not qualified to do it myself. Anybody out there with some good suggestions? -- Thanks.

 

[alldodge]

I have a set of dual carbs (I assume they are Mikunis) with Vortex flame arrestors on my 1994 GTX. The Doo has been sitting for 3 years due to needed repairs. Now I am trying to get it started and it will start with starter fluid, but it runs badly and stalls in low rpm. At midrange to high rpm the engine back fires here and then. I have flushed the carbs with all kinds of miracle products, but the rough running and sputtering is about a good as it gets, I guess. I assume my carbs need a good going over, but I am not qualified to do it myself. Anybody out there with some good suggestions? -- Thanks.

Starting fluid is bad news to rotrax engines, it breaks the reed valves. Pull the plugs and run a compression test, my guess is you now need new valves

 

[Cptobvious]

Starting fluid is bad news to rotrax engines, it breaks the reed valves. Pull the plugs and run a compression test, my guess is you now need new valves

2 stroke seadoo Rotax engines Don't use reed valves(787cc and 951cc motors used rave valves) they use a rotary valve which is essentially a thin semicircle plate that passes over the intake of the cylinders at a specific time relative to the piston stroke to suck in the intake charge.......True using to much starting fluid can wash the oil off the bearings and cylinders inside but a couple squirts here and there won't hurt......your safer using a spritz of premixed gas and oil in place of starter fluid.

There's only 2 types of people that should own jetskis......people that have alot of money....that they don't mind blowing getting screwed at a stealership or those people who want to learn how to fix it themselves......its not hard to learn I promise you....2 strokes are very simple mechanisms.

Your GTX should have a 657cc 80hp motor in it. 2 things I will say to do are 1. Replace all the full lines if they havent already......Go to the hardware store and buy about 15 feet of 1/4" fuel line to do it.....2. Your can get the Mikuni dual carb rebuild kit for less than $45 on ebay......watch the multitude of rebuild videos on youtube that will show you how to rebuild those carbs......thats how I learned

If your compression is 125 or better in both cylinders I wouldnt worry to much about a rebuild right now.....140+- is perfect

Almost forgot.......Download a shop manual for that motor.....everything you want to know about it is in there.

 

[Brian 26]

I'll echo what capt obvious said but with a few edits.

You really should do the carbs yourself. To have them done right at a dealer (if you can find a dealer who will take your ski in) will be a couple hundo, probably about what the ski is currently worth. There are a lot of step by step instruction out there for carb rebuilds.

Don't cheap out on the carb kits, get the real Mikuni kits with needle and seats. The cheap ones are notorious for having bad parts and leaky needle and seats.

As stated change the fuel lines, sounds odd I know but the original fuel lines can destroy the engine (lots of info online).

And please lay off the starting fluid, you're running the motor without oil. Dripping pre mix gas down the spark plug hole is a much better option.

Let us know how it goes.

 

[Rivergator]

Thanks for all your advise, no more starter fluid, makes sense. I started to overhaul the 2 carbs myself. It's actually rediculously simple, but I was apprehensive at first never having done it, but once I opened them up, I realized it's no science. I was told by a top Sea Doo expert that the fuel line used on my 1994 GTX was the good one and not the one that's causing all the problems, but I was going to replace them anyway. I went to Advanced Auto Parts to get the 1/4" fuel line, but the fuel line sold nowadays in parts stores is pretty thick to handle high pressure fuel injection. The OD is much bigger than the original Sea Doo grey fuel line and I am really not too crazy about it (it makes it hard to install in some of the tight places on the Doo). I was told just to go ahead and use the clear plastic tubing. They said it was gasoline proof and since the Sea Doo is not a high pressure fuel system, it would be ideal. What is your take on this???

 

[dannyual767]

I'm glad to hear that you're rebuilding the carbs yourself!

What clear plastic tubing are you talking about? Do you mean the clear plastic tubing found in the plumbing/pipe/hose sections of Lowes and Home Depot? If so, I wouldn't recommend that stuff for long term use with gasoline.

If you're talking about the transparent, colored, "made for use with gas" fuel tubing, well that's a different story. I use it and it's worked well for me for several years. Like you, I didn't like the thickness of the black automotive fuel hose but lots of people use it with no problems. I'm sure the black automotive hose will last longer than my pretty, transparent blue fuel hoses but I still like mine.

 

[Rivergator]

I'm glad to hear that you're rebuilding the carbs yourself!

What clear plastic tubing are you talking about? Do you mean the clear plastic tubing found in the plumbing/pipe/hose sections of Lowes and Home Depot? If so, I wouldn't recommend that stuff for long term use with gasoline.

If you're talking about the transparent, colored, "made for use with gas" fuel tubing, well that's a different story. I use it and it's worked well for me for several years. Like you, I didn't like the thickness of the black automotive fuel hose but lots of people use it with no problems. I'm sure the black automotive hose will last longer than my pretty, transparent blue fuel hoses but I still like mine.

Yeah, that's excatly what I was talking about, the clear vinyl tubing you will get from Lowe's or Home Depot. I did speak to the tech. department of the manufacturer of that vinyl tubing and they said that they have no knowledge of any adverse affects when used with gasoline. Granted, I use it all the time to syphon gas etc. with no problems, but my concerns were long time and uninterrupted contact with gas on my Doo. Where do you get the transparent, colored, "made for use with gas" fuel tubing? I certainly want to look at that too.

 

[dannyual767]

It's been over 3 yrs ago but I'm pretty sure that I got mine from here: http://fuel-line.com/

It's been working good and is still soft and not stiff. The color (blue) has held up pretty well, too. Not that it's very important.

 

[Rivergator]

Thanks for the tip. That fuel line looks and sounds like a great product, just what I was looking for. Here is my plan. Since I was told that my oem fuel line is not the one that causes problems I will not mess with it entirely. I will cut it about 6" away from the carb inlet, install an additional inline fuel filter there and continue out with the new red transparent fuel line to the carb. All the lines connected to the 2 carbs will be the new red line. Now should the old fuel line between the tank and the inline fuel filter develop a problem, the fuel filter will catch it and I can see it.

 

[slag]

If your oem fuel line is gray like you said, then it is the original "tempo" fuel line and yes, it will degrade, separate, and clog the filters in your carbs.

 

[Rivergator]

I just got through rebuilding the dual carbs on my 1994 GTX and I must admit, it's not running well. it seems to run very well on the trailer, no sputtering, no misfiring and good throttle response. This morning I put it out in the water and I had a little difficulty getting it started, because the primer pump is not up to snuff. I squirted some gas into the carbs and it started. But here is what it does: It idles fine I would say. At first it did not want to accelerate when I pulled the throttle, but wanted to stall. After several restarts and careful manipulation of the throttle I finally got it to go into higher RPM doing about 15 miles/hr and then I went to WOT, but the RPM did NOT increase. I was cruising along in WOT doing about 15 miles/h. Engine acted just fine, no misfiring, sputtering, coughing etc. It acted like I was running on half throttle, even though I was doing WOT. Without doing anything else, cruising along at 15 miles/h throttle wide open, about a minute later or sometimes 2 all of a sudden, the RPM starts to pick up and I am doing 30-35 miles/h. and would continue to do so for as long as I don't let up on the throttle. The minute I let the throttle go and then I go back WOT again the same thing repeats. I cruise along at 15 and then a few minutes later it goes into high gear again. I did this for a couple of hours, thinking that everything needs to be exercised and broken in but in the end it would not rev up anymore. It stayed at around 15 miles/h until I turned the engine off. The 15 mile speed is very steady, no pulsating, it almost feels like a speed limiter is keeping it there. I must also add that the doo did not run for 3 years because of other issues, which are all fixed now. There was about a gallon or less of old gas in the tank which was treated before storage. I did treat it again this time and added 3 gallons of fresh 89 octane non-ethanol marine gas to it. I don't think the gas has anything to do with this, but you tell me.

 

[Rivergator]

​In retrospect I did a good job on the carb rebuild. That's not where the problem was. After fixing myself a triple Southern Comfort on the rocks I did some serious analytical thinking and came to the conclusion that one of the 2 cylinders was not doing its job. One had to overcome the dead weight of the other. I knew that the compression was good, so I started with the most simple and least expensive test. Replace both plugs and make sure they both got fire, which they did. I hooked up the Doo and off to the river I went. Oh boy did that baby go, like a bat straight out of hell. I thought that thing was gonna slip out from under my butt. So this Memorial Day weekend we will spend a lot of time on dog river having a great time. The weather is PERFECT. Nothing can go wrong now! Well let?s hope.
I guess I am going to close the thread, because with y?alls help and good advise all my problems (Sea Doo wise, that is) have been solved. Thanks again and y?all have a great summer. -- Rick